clw_uk wrote:
Why is it considered taboo to openly criticise another persons religion in most societies but yet perfectly ok to criticise a persons political convictions?

It really depends on the culture you live in. In France for example, three main topics are supposed to be avoided when having lunch with other people: religion, politics, and money (it's impolite to talk about how much you earn or how much you paid for your car for example).
Of course things are slightly different when you talk with close family members or close friends.

Here in the US, politics is, as always has been, something we try to convince each other. Debates, town square meetings, advertisements. I don't see anything odd about people discussing and debating and arguing about what is the right way to govern. The whole point of a democracy is government by the people; the people can't govern if they can't discuss. US government is founded on the idea of people feeling free to talk about it.

Religion in the US is founded on the idea of escaping persecution, the idea that people would be free to practice how they want without interference. So there is no place for debate or discussion, except perhaps amongst close friends. I would find it very rude if you came up to me out of the blue and tried to argue with me that my religious practices were wrong.

And yes, theoretically at least, we debate political ideas because we can look at what we've done and look at the results and try to learn from that. But arguing over what happens after we die (the main topic of most religions) is kinda pointless since we have no data to argue over.